If you already have a 1000mAh, 4.8volt AA battery pack, you already have your ignition. There is little or no benefit to running li-ons on the ignition. You may shave a few grams, but have offsets in cost and accessories. There is also no benefit to running higher than 4.8 volts on the ignition.

If and when you decide to go with lithiums, think about contacting a manufacturer or distributer that markets a matched system, charger included.